Inkjet Nozzle Arrangement Having Interleaved Heater Elements

ABSTRACT

An inkjet nozzle arrangement is provided having a wafer defining an ink chamber for holding ink and a chamber roof covering the ink chamber. The chamber roof has an ink ejection port supported by a plurality of outwardly extending bridge members and a plurality of elongate heater elements interleaved between the bridge members for causing ejection of ink held in the ink chamber through the ink ejection port.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No. 11/706,379 filed Feb. 15, 2007, which is a continuation application of U.S. application Ser. No. 11/026,136 filed Jan. 3, 2005, now issued U.S. Pat. No. 7,188,933, which is a continuation application of U.S. application Ser. No. 10/309,036 filed Dec. 4, 2002, now issued U.S. Pat. No. 7,284,833, which is a Continuation Application of U.S. application Ser. No. 09/855,093 filed May 14, 2001, now issued U.S. Pat. No. 6,505,912, which is a Continuation Application of U.S. application Ser. No. 09/112,806 filed Jul. 10, 1998, now issued U.S. Pat. No. 6,247,790 all of which are herein incorporated by reference.

The following Australian provisional patent applications are hereby incorporated by cross-reference. For the purposes of location and identification, US patents/patent applications identified by their US patent/patent application serial numbers are listed alongside the Australian applications from which the US patents/patent applications claim the right of priority.

US PATENT/ CROSS-REFERENCED PATENT APPLICATION AUSTRALIAN (CLAIMING RIGHT PROVISIONAL OF PRIORITY FROM PATENT AUSTRALIAN PROVISIONAL DOCKET APPLICATION NO. APPLICATION) NO. PO7991 6,750,901 ART01US PO8505 6,476,863 ART02US PO7988 6,788,336 ART03US PO9395 6,322,181 ART04US PO8017 6,597,817 ART06US PO8014 6,227,648 ART07US PO8025 6,727,948 ART08US PO8032 6,690,419 ART09US PO7999 6,727,951 ART10US PO8030 6,196,541 ART13US PO7997 6,195,150 ART15US PO7979 6,362,868 ART16US PO7978 6,831,681 ART18US PO7982 6,431,669 ART19US PO7989 6,362,869 ART20US PO8019 6,472,052 ART21US PO7980 6,356,715 ART22US PO8018 6,894,694 ART24US PO7938 6,636,216 ART25US PO8016 6,366,693 ART26US PO8024 6,329,990 ART27US PO7939 6,459,495 ART29US PO8501 6,137,500 ART30US PO8500 6,690,416 ART31US PO7987 7,050,143 ART32US PO8022 6,398,328 ART33US PO8497 7,110,024 ART34US PO8020 6,431,704 ART38US PO8504 6,879,341 ART42US PO8000 6,415,054 ART43US PO7934 6,665,454 ART45US PO7990 6,542,645 ART46US PO8499 6,486,886 ART47US PO8502 6,381,361 ART48US PO7981 6,317,192 ART50US PO7986 6,850,274 ART51US PO7983 09/113,054 ART52US PO8026 6,646,757 ART53US PO8028 6,624,848 ART56US PO9394 6,357,135 ART57US PO9397 6,271,931 ART59US PO9398 6,353,772 ART60US PO9399 6,106,147 ART61US PO9400 6,665,008 ART62US PO9401 6,304,291 ART63US PO9403 6,305,770 ART65US PO9405 6,289,262 ART66US PP0959 6,315,200 ART68US PP1397 6,217,165 ART69US PP2370 6,786,420 DOT01US PO8003 6,350,023 Fluid01US PO8005 6,318,849 Fluid02US PO8066 6,227,652 IJ01US PO8072 6,213,588 IJ02US PO8040 6,213,589 IJ03US PO8071 6,231,163 IJ04US PO8047 6,247,795 IJ05US PO8035 6,394,581 IJ06US PO8044 6,244,691 IJ07US PO8063 6,257,704 IJ08US PO8057 6,416,168 IJ09US PO8056 6,220,694 IJ10US PO8069 6,257,705 IJ11US PO8049 6,247,794 IJ12US PO8036 6,234,610 IJ13US PO8048 6,247,793 IJ14US PO8070 6,264,306 IJ15US PO8067 6,241,342 IJ16US PO8001 6,247,792 IJ17US PO8038 6,264,307 IJ18US PO8033 6,254,220 IJ19US PO8002 6,234,611 IJ20US PO8068 6,302,528 IJ21US PO8062 6,283,582 IJ22US PO8034 6,239,821 IJ23US PO8039 6,338,547 IJ24US PO8041 6,247,796 IJ25US PO8004 6,557,977 IJ26US PO8037 6,390,603 IJ27US PO8043 6,362,843 IJ28US PO8042 6,293,653 IJ29US PO8064 6,312,107 IJ30US PO9389 6,227,653 IJ31US PO9391 6,234,609 IJ32US PP0888 6,238,040 IJ33US PP0891 6,188,415 IJ34US PP0890 6,227,654 IJ35US PP0873 6,209,989 IJ36US PP0993 6,247,791 IJ37US PP0890 6,336,710 IJ38US PP1398 6,217,153 IJ39US PP2592 6,416,167 IJ40US PP2593 6,243,113 IJ41US PP3991 6,283,581 IJ42US PP3987 6,247,790 IJ43US PP3985 6,260,953 IJ44US PP3983 6,267,469 IJ45US PO7935 6,224,780 IJM01US PO7936 6,235,212 IJM02US PO7937 6,280,643 IJM03US PO8061 6,284,147 IJM04US PO8054 6,214,244 IJM05US PO8065 6,071,750 IJM06US PO8055 6,267,905 IJM07US PO8053 6,251,298 IJM08US PO8078 6,258,285 IJM09US PO7933 6,225,138 IJM10US PO7950 6,241,904 IJM11US PO7949 6,299,786 IJM12US PO8060 6,866,789 IJM13US PO8059 6,231,773 IJM14US PO8073 6,190,931 IJM15US PO8076 6,248,249 IJM16US PO8075 6,290,862 IJM17US PO8079 6,241,906 IJM18US PO8050 6,565,762 IJM19US PO8052 6,241,905 IJM20US PO7948 6,451,216 IJM21US PO7951 6,231,772 IJM22US PO8074 6,274,056 IJM23US PO7941 6,290,861 IJM24US PO8077 6,248,248 IJM25US PO8058 6,306,671 IJM26US PO8051 6,331,258 IJM27US PO8045 6,110,754 IJM28US PO7952 6,294,101 IJM29US PO8046 6,416,679 IJM30US PO9390 6,264,849 IJM31US PO9392 6,254,793 IJM32US PP0889 6,235,211 IJM35US PP0887 6,491,833 IJM36US PP0882 6,264,850 IJM37US PP0874 6,258,284 IJM38US PP1396 6,312,615 IJM39US PP3989 6,228,668 IJM40US PP2591 6,180,427 IJM41US PP3990 6,171,875 IJM42US PP3986 6,267,904 IJM43US PP3984 6,245,247 IJM44US PP3982 6,315,914 IJM45US PP0895 6,231,148 IR01US PP0869 6,293,658 IR04US PP0887 6,614,560 IR05US PP0885 6,238,033 IR06US PP0884 6,312,070 IR10US PP0886 6,238,111 IR12US PP0877 6,378,970 IR16US PP0878 6,196,739 IR17US PP0883 6,270,182 IR19US PP0880 6,152,619 IR20US PO8006 6,087,638 MEMS02US PO8007 6,340,222 MEMS03US PO8010 6,041,600 MEMS05US PO8011 6,299,300 MEMS06US PO7947 6,067,797 MEMS07US PO7944 6,286,935 MEMS09US PO7946 6,044,646 MEMS10US PP0894 6,382,769 MEMS13US

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

FIELD OF THE INVENTION

The present invention relates to the field of fluid ejection and, in particular, discloses a fluid ejection chip.

BACKGROUND OF THE INVENTION

Many different types of printing mechanisms have been invented, a large number of which are presently in use. The known forms of printers have a variety of methods for marking the print media with a relevant marking media. Commonly used forms of printing include offset printing, laser printing and copying devices, dot matrix type impact printers, thermal paper printers, film recorders, thermal wax printers, dye sublimation printers and ink jet printers both of the drop on demand and continuous flow type. Each type of printer has its own advantages and problems when considering cost, speed, quality, reliability, simplicity of construction and operation etc.

In recent years the field of ink jet printing, wherein each individual pixel of ink is derived from one or more ink nozzles, has become increasingly popular primarily due to its inexpensive and versatile nature.

Many different techniques of ink jet printing have been invented. For a survey of the field, reference is made to an article by J Moore, “Non-Impact Printing: Introduction and Historical Perspective”, Output Hard Copy Devices, Editors R Dubeck and S Sherr, pages 207-220 (1988).

Ink Jet printers themselves come in many different forms. The utilization of a continuous stream of ink in ink jet printing appears to date back to at least 1929 wherein U.S. Pat. No. 1,941,001 by Hansell discloses a simple form of continuous stream electro-static ink jet printing.

U.S. Pat. No. 3,596,275 by Sweet also discloses a process of a continuous ink jet printing including a step wherein the ink jet stream is modulated by a high frequency electro-static field so as to cause drop separation. This technique is still utilized by several manufacturers including Elmjet and Scitex (see also U.S. Pat. No. 3,373,437 by Sweet et al).

Piezoelectric ink jet printers are also one form of commonly utilized ink jet printing device. Piezoelectric systems are disclosed by Kyser et. al. in U.S. Pat. No. 3,946,398 (1970) which utilizes a diaphragm mode of operation, by Zolten in U.S. Pat. No. 3,683,212 (1970) which discloses a squeeze mode form of operation of a piezoelectric crystal, Stemme in U.S. Pat. No. 3,747,120 (1972) which discloses a bend mode of piezoelectric operation, Howkins in U.S. Pat. No. 4,459,601 which discloses a piezoelectric push mode actuation of the ink jet stream and Fischbeck in U.S. Pat. No. 4,584,590 which discloses a shear mode type of piezoelectric transducer element.

Recently, thermal ink jet printing has become an extremely popular form of ink jet printing. The ink jet printing techniques include those disclosed by Endo et al in GB 2007162 (1979) and Vaught et al in U.S. Pat. No. 4,490,728. Both the aforementioned references disclose ink jet printing techniques which rely on the activation of an electrothermal actuator which results in the creation of a bubble in a constricted space, such as a nozzle, which thereby causes the ejection of ink from an aperture connected to the confined space onto a relevant print media. Manufacturers such as Canon and Hewlett Packard manufacture printing devices utilizing the electro-thermal actuator.

As can be seen from the foregoing, many different types of printing technologies are available. Ideally, a printing technology should have a number of desirable attributes. These include inexpensive construction and operation, high-speed operation, safe and continuous long-term operation etc. Each technology may have its own advantages and disadvantages in the areas of cost, speed, quality, reliability, power usage, simplicity of construction and operation, durability and consumables.

Applicant has developed a substantial amount of technology in the field of micro-electromechanical inkjet printing. The parent application is indeed directed to a particular aspect in this field. In this application, the Applicant has applied the technology to the more general field of fluid ejection.

SUMMARY OF THE INVENTION

In accordance with a first aspect of the present invention, there is provided a nozzle arrangement for an ink jet printhead, the arrangement comprising a nozzle chamber defined in a wafer substrate for the storage of ink to be ejected; an ink ejection port having a rim formed on one wall of the chamber; and a series of actuators attached to the wafer substrate, and forming a portion of the wall of the nozzle chamber adjacent the rim, the actuator paddles further being actuated in unison so as to eject ink from the nozzle chamber via the ink ejection nozzle.

The actuators can include a surface which bends inwards away from the center of the nozzle chamber upon actuation. The actuators are preferably actuated by means of a thermal actuator device. The thermal actuator device may comprise a conductive resistive heating element encased within a material having a high coefficient of thermal expansion. The element can be serpentine to allow for substantially unhindered expansion of the material. The actuators are preferably arranged radially around the nozzle rim.

The actuators can form a membrane between the nozzle chamber and an external atmosphere of the arrangement and the actuators bend away from the external atmosphere to cause an increase in pressure within the nozzle chamber thereby initiating a consequential ejection of ink from the nozzle chamber. The actuators can bend away from a central axis of the nozzle chamber.

The nozzle arrangement can be formed on the wafer substrate utilizing micro-electro mechanical techniques and further can comprise an ink supply channel in communication with the nozzle chamber. The ink supply channel may be etched through the wafer. The nozzle arrangement may include a series of struts which support the nozzle rim.

The arrangement can be formed adjacent to neighbouring arrangements so as to form a pagewidth printhead.

In this application, the invention extends to a fluid ejection chip that comprises

a substrate; and

a plurality of nozzle arrangements positioned on the substrate, each nozzle arrangement comprising

-   -   a nozzle chamber defining structure which defines a nozzle         chamber and which includes a wall in which a fluid ejection port         is defined; and     -   at least one actuator for ejecting fluid from the nozzle chamber         through the fluid ejection port, the, or each, actuator being         displaceable with respect to the substrate on receipt of an         electrical signal, wherein     -   the, or each, actuator is formed in said wall of the nozzle         chamber defining structure, so that displacement of the, or         each, actuator results in a change in volume of the nozzle         chamber so that fluid is ejected from the fluid ejection port.

Each nozzle arrangement may include a plurality of actuators, each actuator including an actuating portion and a paddle positioned on the actuating portion, the actuating portion being anchored to the substrate and being displaceable on receipt of an electrical signal to displace the paddle, in turn, the paddles and the wall being substantially coplanar and the actuating portions being configured so that, upon receipt of said electrical signal, the actuating portions displace the paddles into the nozzle chamber to reduce a volume of the nozzle chamber, thereby ejecting fluid from the fluid ejection port.

A periphery of each paddle may be shaped to define a fluidic seal when the nozzle chamber is filled with fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

Notwithstanding any other forms which may fall within the scope of the present invention, preferred forms of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

FIGS. 1-3 are schematic sectional views illustrating the operational principles of the preferred embodiment;

FIG. 4( a) and FIG. 4( b) are again schematic sections illustrating the operational principles of the thermal actuator device;

FIG. 5 is a side perspective view, partly in section, of a single nozzle arrangement constructed in accordance with the preferred embodiments;

FIGS. 6-13 are side perspective views, partly in section, illustrating the manufacturing steps of the preferred embodiments;

FIG. 14 illustrates an array of ink jet nozzles formed in accordance with the manufacturing procedures of the preferred embodiment;

FIG. 15 provides a legend of the materials indicated in FIGS. 16 to 23; and

FIG. 16 to FIG. 23 illustrate sectional views of the manufacturing steps in one form of construction of a nozzle arrangement in accordance with the invention.

DESCRIPTION OF PREFERRED AND OTHER EMBODIMENTS

In the following description, reference is made to the ejection of ink for application to ink jet printing. However, it will readily be appreciated that the present application can be applied to any situation where fluid ejection is required.

In the preferred embodiment, ink is ejected out of a nozzle chamber via an ink ejection port using a series of radially positioned thermal actuator devices that are arranged about the ink ejection port and are activated to pressurize the ink within the nozzle chamber thereby causing the ejection of ink through the ejection port.

Turning now to FIGS. 1, 2 and 3, there is illustrated the basic operational principles of the preferred embodiment. FIG. 1 illustrates a single nozzle arrangement 1 in its quiescent state. The arrangement 1 includes a nozzle chamber 2 which is normally filled with ink so as to form a meniscus 3 in an ink ejection port 4. The nozzle chamber 2 is formed within a wafer 5. The nozzle chamber 2 is supplied with ink via an ink supply channel 6 which is etched through the wafer 5 with a highly isotropic plasma etching system. A suitable etcher can be the Advance Silicon Etch (ASE) system available from Surface Technology Systems of the United Kingdom.

A top of the nozzle arrangement 1 includes a series of radially positioned actuators 8, 9. These actuators comprise a polytetrafluoroethylene (PTFE) layer and an internal serpentine copper core 17. Upon heating of the copper core 17, the surrounding PTFE expands rapidly resulting in a generally downward movement of the actuators 8, 9. Hence, when it is desired to eject ink from the ink ejection port 4, a current is passed through the actuators 8, 9 which results in them bending generally downwards as illustrated in FIG. 2. The downward bending movement of the actuators 8, 9 results in a substantial increase in pressure within the nozzle chamber 2. The increase in pressure in the nozzle chamber 2 results in an expansion of the meniscus 3 as illustrated in FIG. 2.

The actuators 8, 9 are activated only briefly and subsequently deactivated. Consequently, the situation is as illustrated in FIG. 3 with the actuators 8, 9 returning to their original positions. This results in a general inflow of ink back into the nozzle chamber 2 and a necking and breaking of the meniscus 3 resulting in the ejection of a drop 12. The necking and breaking of the meniscus 3 is a consequence of the forward momentum of the ink associated with drop 12 and the backward pressure experienced as a result of the return of the actuators 8, 9 to their original positions. The return of the actuators 8,9 also results in a general inflow of ink from the channel 6 as a result of surface tension effects and, eventually, the state returns to the quiescent position as illustrated in FIG. 1.

FIGS. 4( a) and 4(b) illustrate the principle of operation of the thermal actuator. The thermal actuator is preferably constructed from a material 14 having a high coefficient of thermal expansion. Embedded within the material 14 are a series of heater elements 15 which can be a series of conductive elements designed to carry a current. The conductive elements 15 are heated by passing a current through the elements 15 with the heating resulting in a general increase in temperature in the area around the heating elements 15. The position of the elements 15 is such that uneven heating of the material 14 occurs. The uneven increase in temperature causes a corresponding uneven expansion of the material 14. Hence, as illustrated in FIG. 4( b), the PTFE is bent generally in the direction shown.

In FIG. 5, there is illustrated a side perspective view of one embodiment of a nozzle arrangement constructed in accordance with the principles previously outlined. The nozzle chamber 2 is formed with an isotropic surface etch of the wafer 5. The wafer 5 can include a CMOS layer including all the required power and drive circuits. Further, the actuators 8, 9 each have a leaf or petal formation which extends towards a nozzle rim 28 defining the ejection port 4. The normally inner end of each leaf or petal formation is displaceable with respect to the nozzle rim 28. Each activator 8, 9 has an internal copper core 17 defining the element 15. The core 17 winds in a serpentine manner to provide for substantially unhindered expansion of the actuators 8, 9. The operation of the actuators 8, 9 is as illustrated in FIG. 4( a) and FIG. 4( b) such that, upon activation, the actuators 8 bend as previously described resulting in a displacement of each petal formation away from the nozzle rim 28 and into the nozzle chamber 2. The ink supply channel 6 can be created via a deep silicon back edge of the wafer 5 utilizing a plasma etcher or the like. The copper or aluminum core 17 can provide a complete circuit. A central arm 18 which can include both metal and PTFE portions provides the main structural support for the actuators 8, 9.

Turning now to FIG. 6 to FIG. 13, one form of manufacture of the nozzle arrangement 1 in accordance with the principles of the preferred embodiment is shown. The nozzle arrangement 1 is preferably manufactured using micro-electromechanical (MEMS) techniques and can include the following construction techniques:

As shown initially in FIG. 6, the initial processing starting material is a standard semi-conductor wafer 20 having a complete CMOS level 21 to a first level of metal. The first level of metal includes portions 22 which are utilized for providing power to the thermal actuators 8, 9.

The first step, as illustrated in FIG. 7, is to etch a nozzle region down to the silicon wafer 20 utilizing an appropriate mask.

Next, as illustrated in FIG. 8, a 2 μm layer of polytetrafluoroethylene (PTFE) is deposited and etched so as to define vias 24 for interconnecting multiple levels.

Next, as illustrated in FIG. 9, the second level metal layer is deposited, masked and etched to define a heater structure 25. The heater structure 25 includes via 26 interconnected with a lower aluminum layer.

Next, as illustrated in FIG. 10, a further 2 μm layer of PTFE is deposited and etched to the depth of 1 μm utilizing a nozzle rim mask to define the nozzle rim 28 in addition to ink flow guide rails 29 which generally restrain any wicking along the surface of the PTFE layer. The guide rails 29 surround small thin slots and, as such, surface tension effects are a lot higher around these slots which in turn results in minimal outflow of ink during operation.

Next, as illustrated in FIG. 11, the PTFE is etched utilizing a nozzle and actuator mask to define a port portion 30 and slots 31 and 32.

Next, as illustrated in FIG. 12, the wafer is crystallographically etched on a <111> plane utilizing a standard crystallographic etchant such as KOH. The etching forms a chamber 33, directly below the port portion 30.

In FIG. 13, the ink supply channel 34 can be etched from the back of the wafer utilizing a highly anisotropic etcher such as the STS etcher from Silicon Technology Systems of United Kingdom. An array of ink jet nozzles can be formed simultaneously with a portion of an array 36 being illustrated in FIG. 14. A portion of the printhead is formed simultaneously and diced by the STS etching process. The array 36 shown provides for four column printing with each separate column attached to a different color ink supply channel being supplied from the back of the wafer. Bond pads 37 provide for electrical control of the ejection mechanism.

In this manner, large pagewidth printheads can be fabricated so as to provide for a drop-on-demand ink ejection mechanism.

One form of detailed manufacturing process which can be used to fabricate monolithic ink jet printheads operating in accordance with the principles taught by the present embodiment can proceed utilizing the following steps:

1. Using a double-sided polished wafer 60, complete a 0.5 micron, one poly, 2 metal CMOS process 61. This step is shown in FIG. 16. For clarity, these diagrams may not be to scale, and may not represent a cross section though any single plane of the nozzle. FIG. 15 is a key to representations of various materials in these manufacturing diagrams, and those of other cross-referenced ink jet configurations.

2. Etch the CMOS oxide layers down to silicon or second level metal using Mask 1. This mask defines the nozzle cavity and the edge of the chips. This step is shown in FIG. 16.

3. Deposit a thin layer (not shown) of a hydrophilic polymer, and treat the surface of this polymer for PTFE adherence.

4. Deposit 1.5 microns of polytetrafluoroethylene (PTFE) 62.

5. Etch the PTFE and CMOS oxide layers to second level metal using Mask 2. This mask defines the contact vias for the heater electrodes. This step is shown in FIG. 17.

6. Deposit and pattern 0.5 microns of gold 63 using a lift-off process using Mask 3. This mask defines the heater pattern. This step is shown in FIG. 18.

7. Deposit 1.5 microns of PTFE 64.

8. Etch 1 micron of PTFE using Mask 4. This mask defines the nozzle rim 65 and the rim at the edge 66 of the nozzle chamber. This step is shown in FIG. 19.

9. Etch both layers of PTFE and the thin hydrophilic layer down to silicon using Mask 5. This mask defines a gap 67 at inner edges of the actuators, and the edge of the chips. It also forms the mask for a subsequent crystallographic etch. This step is shown in FIG. 20.

10. Crystallographically etch the exposed silicon using KOH. This etch stops on <111> crystallographic planes 68, forming an inverted square pyramid with sidewall angles of 54.74 degrees. This step is shown in FIG. 21.

11. Back-etch through the silicon wafer (with, for example, an ASE Advanced Silicon Etcher from Surface Technology Systems) using Mask 6. This mask defines the ink inlets 69 which are etched through the wafer. The wafer is also diced by this etch. This step is shown in FIG. 22.

12. Mount the printheads in their packaging, which may be a molded plastic former incorporating ink channels which supply the appropriate color ink to the ink inlets 69 at the back of the wafer.

13. Connect the printheads to their interconnect systems. For a low profile connection with minimum disruption of airflow, TAB may be used. Wire bonding may also be used if the printer is to be operated with sufficient clearance to the paper.

14. Fill the completed print heads with ink 70 and test them. A filled nozzle is shown in FIG. 23.

The presently disclosed ink jet printing technology is potentially suited to a wide range of printing systems including: color and monochrome office printers, short run digital printers, high speed digital printers, offset press supplemental printers, low cost scanning printers high speed pagewidth printers, notebook computers with inbuilt pagewidth printers, portable color and monochrome printers, color and monochrome copiers, color and monochrome facsimile machines, combined printer, facsimile and copying machines, label printers, large format plotters, photograph copiers, printers for digital photographic “minilabs”, video printers, PHOTO CD (PHOTO CD is a registered trade mark of the Eastman Kodak Company) printers, portable printers for PDAs, wallpaper printers, indoor sign printers, billboard printers, fabric printers, camera printers and fault tolerant commercial printer arrays.

It would be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.

Ink Jet Technologies

The embodiments of the invention use an ink jet printer type device. Of course many different devices could be used. However, presently popular ink jet printing technologies are unlikely to be suitable.

The most significant problem with thermal ink jet is power consumption. This is approximately 100 times that required for high speed, and stems from the energy-inefficient means of drop ejection. This involves the rapid boiling of water to produce a vapor bubble which expels the ink. Water has a very high heat capacity, and must be superheated in thermal ink jet applications. This leads to an efficiency of around 0.02%, from electricity input to drop momentum (and increased surface area) out.

The most significant problem with piezoelectric ink jet is size and cost. Piezoelectric crystals have a very small deflection at reasonable drive voltages, and therefore require a large area for each nozzle. Also, each piezoelectric actuator must be connected to its drive circuit on a separate substrate. This is not a significant problem at the current limit of around 300 nozzles per printhead, but is a major impediment to the fabrication of pagewidth printheads with 19,200 nozzles.

Ideally, the ink jet technologies used meet the stringent requirements of in-camera digital color printing and other high quality, high speed, low cost printing applications. To meet the requirements of digital photography, new ink jet technologies have been created. The target features include:

low power (less than 10 Watts)

High-resolution capability (1,600 dpi or more)

photographic quality output

low manufacturing cost

small size (pagewidth times minimum cross section)

high speed (<2 seconds per page).

All of these features can be met or exceeded by the ink jet systems described below with differing levels of difficulty. Forty-five different ink jet technologies have been developed by the Assignee to give a wide range of choices for high volume manufacture. These technologies form part of separate applications assigned to the present Assignee as set out in the table below under the heading Cross References to Related Applications.

The ink jet designs shown here are suitable for a wide range of digital printing systems, from battery powered one-time use digital cameras, through to desktop and network printers, and through to commercial printing systems.

For ease of manufacture using standard process equipment, the printhead is designed to be a monolithic 0.5-micron CMOS chip with MEMS post processing. For color photographic applications, the printhead is 100 mm long, with a width which depends upon the ink jet type. The smallest printhead designed is IJ38, which is 0.35 mm wide, giving a chip area of 35 square mm. The printheads each contain 19,200 nozzles plus data and control circuitry.

Ink is supplied to the back of the printhead by injection molded plastic ink channels. The molding requires 50 micron features, which can be created using a lithographically micromachined insert in a standard injection molding tool. Ink flows through holes etched through the wafer to the nozzle chambers fabricated on the front surface of the wafer. The printhead is connected to the camera circuitry by tape automated bonding.

Tables of Drop-on-Demand Ink Jets

Eleven important characteristics of the fundamental operation of individual ink jet nozzles have been identified. These characteristics are largely orthogonal, and so can be elucidated as an eleven dimensional matrix. Most of the eleven axes of this matrix include entries developed by the present assignee.

The following tables form the axes of an eleven dimensional table of ink jet types.

Actuator mechanism (18 types)

Basic operation mode (7 types)

Auxiliary mechanism (8 types)

Actuator amplification or modification method (17 types)

Actuator motion (19 types)

Nozzle refill method (4 types)

Method of restricting back-flow through inlet (10 types)

Nozzle clearing method (9 types)

Nozzle plate construction (9 types)

Drop ejection direction (5 types)

Ink type (7 types)

The complete eleven dimensional table represented by these axes contains 36.9 billion possible configurations of ink jet nozzle. While not all of the possible combinations result in a viable ink jet technology, many million configurations are viable. It is clearly impractical to elucidate all of the possible configurations. Instead, certain ink jet types have been investigated in detail. These are designated IJ01 to IJ45 above which matches the docket numbers in the table under the heading Cross References to Related Applications.

Other ink jet configurations can readily be derived from these forty-five examples by substituting alternative configurations along one or more of the 11 axes. Most of the IJ01 to IJ45 examples can be made into ink jet printheads with characteristics superior to any currently available ink jet technology.

Where there are prior art examples known to the inventor, one or more of these examples are listed in the examples column of the tables below. The IJ01 to IJ45 series are also listed in the examples column. In some cases, print technology may be listed more than once in a table, where it shares characteristics with more than one entry.

Suitable applications for the ink jet technologies include: Home printers, Office network printers, Short run digital printers, Commercial print systems, Fabric printers, Pocket printers, Internet WWW printers, Video printers, Medical imaging, Wide format printers, Notebook PC printers, Fax machines, Industrial printing systems, Photocopiers, Photographic minilabs etc.

The information associated with the aforementioned 11 dimensional matrix is set out in the following tables.

ACTUATOR MECHANISM (APPLIED ONLY TO SELECTED INK DROPS) Description Advantages Disadvantages Examples Thermal An electrothermal Large High Canon bubble heater heats the force generated power Bubblejet 1979 ink to above Simple Ink carrier Endo et al GB boiling point, construction limited to water patent 2,007,162 transferring No Low Xerox significant heat to moving parts efficiency heater-in-pit the aqueous ink. A Fast High 1990 Hawkins et bubble nucleates operation temperatures al U.S. Pat. No. and quickly forms, Small chip required 4,899,181 expelling the ink. area required for High Hewlett- The efficiency of actuator mechanical Packard TIJ the process is low, stress 1982 Vaught et with typically less Unusual al U.S. Pat. No. than 0.05% of the materials 4,490,728 electrical energy required being transformed Large into kinetic energy drive transistors of the drop. Cavitation causes actuator failure Kogation reduces bubble formation Large print heads are difficult to fabricate Piezo- A piezoelectric Low Very large Kyser et al electric crystal such as power area required for U.S. Pat. No. 3,946,398 lead lanthanum consumption actuator Zoltan zirconate (PZT) is Many ink Difficult U.S. Pat. No. 3,683,212 electrically types can be to integrate with 1973 activated, and used electronics Stemme U.S. Pat. No. either expands, Fast High 3,747,120 shears, or bends to operation voltage drive Epson apply pressure to High transistors Stylus the ink, ejecting efficiency required Tektronix drops. Full IJ04 page width print heads impractical due to actuator size Requires electrical poling in high field strengths during manufacture Electro- An electric field is Low Low Seiko strictive used to activate power maximum strain Epson, Usui et electrostriction in consumption (approx. 0.01%) all JP 253401/96 relaxor materials Many ink Large area IJ04 such as lead types can be required for lanthanum used actuator due to zirconate titanate Low low strain (PLZT) or lead thermal Response magnesium expansion speed is niobate (PMN). Electric marginal (~10 μs) field strength High required voltage drive (approx. 3.5 V/μm) transistors can be required generated Full without page width print difficulty heads Does not impractical due require electrical to actuator size poling Ferro- An electric field is Low Difficult IJ04 electric used to induce a power to integrate with phase transition consumption electronics between the Many ink Unusual antiferroelectric types can be materials such as (AFE) and used PLZSnT are ferroelectric (FE) Fast required phase. Perovskite operation (<1 μs) Actuators materials such as Relatively require a large tin modified lead high longitudinal area lanthanum strain zirconate titanate High (PLZSnT) exhibit efficiency large strains of up Electric to 1% associated field strength of with the AFE to around 3 V/μm FE phase can be readily transition. provided Electro- Conductive plates Low Difficult IJ02, IJ04 static are separated by a power to operate plates compressible or consumption electrostatic fluid dielectric Many ink devices in an (usually air). Upon types can be aqueous application of a used environment voltage, the plates Fast The attract each other operation electrostatic and displace ink, actuator will causing drop normally need to ejection. The be separated conductive plates from the ink may be in a comb Very large or honeycomb area required to structure, or achieve high stacked to increase forces the surface area High and therefore the voltage drive force. transistors may be required Full page width print heads are not competitive due to actuator size Electro- A strong electric Low High 1989 Saito static pull field is applied to current voltage required et al, U.S. Pat. No. on ink the ink, whereupon consumption May be 4,799,068 electrostatic Low damaged by 1989 Miura attraction temperature sparks due to air et al, U.S. Pat. No. accelerates the ink breakdown 4,810,954 towards the print Required Tone-jet medium. field strength increases as the drop size decreases High voltage drive transistors required Electrostatic field attracts dust Permanent An electromagnet Low Complex IJ07, IJ10 magnet directly attracts a power fabrication electro- permanent magnet, consumption Permanent magnetic displacing ink and Many ink magnetic causing drop types can be material such as ejection. Rare used Neodymium Iron earth magnets with Fast Boron (NdFeB) a field strength operation required. around 1 Tesla can High High local be used. Examples efficiency currents required are: Samarium Easy Copper Cobalt (SaCo) and extension from metalization magnetic materials single nozzles to should be used in the neodymium page width print for long iron boron family heads electromigration (NdFeB, lifetime and low NdDyFeBNb, resistivity NdDyFeB, etc) Pigmented inks are usually infeasible Operating temperature limited to the Curie temperature (around 540 K) Soft A solenoid Low Complex IJ01, IJ05, magnetic induced a power fabrication IJ08, IJ10, IJ12, core magnetic field in a consumption Materials IJ14, IJ15, IJ17 electro- soft magnetic core Many ink not usually magnetic or yoke fabricated types can be present in a from a ferrous used CMOS fab such material such as Fast as NiFe, electroplated iron operation CoNiFe, or CoFe alloys such as High are required CoNiFe [1], CoFe, efficiency High local or NiFe alloys. Easy currents required Typically, the soft extension from Copper magnetic material single nozzles to metalization is in two parts, page width print should be used which are heads for long normally held electromigration apart by a spring. lifetime and low When the solenoid resistivity is actuated, the two Electroplating parts attract, is required displacing the ink. High saturation flux density is required (2.0-2.1 T is achievable with CoNiFe [1]) Lorenz The Lorenz force Low Force acts IJ06, IJ11, force acting on a current power as a twisting IJ13, IJ16 carrying wire in a consumption motion magnetic field is Many ink Typically, utilized. types can be only a quarter of This allows the used the solenoid magnetic field to Fast length provides be supplied operation force in a useful externally to the High direction print head, for efficiency High local example with rare Easy currents required earth permanent extension from Copper magnets. single nozzles to metalization Only the current page width print should be used carrying wire need heads for long be fabricated on electromigration the print head, lifetime and low simplifying resistivity materials Pigmented requirements. inks are usually infeasible Magneto- The actuator uses Many ink Force acts Fischenbeck, striction the giant types can be as a twisting U.S. Pat. No. magnetostrictive used motion 4,032,929 effect of materials Fast Unusual IJ25 such as Terfenol-D operation materials such as (an alloy of Easy Terfenol-D are terbium, extension from required dysprosium and single nozzles to High local iron developed at page width print currents required the Naval heads Copper Ordnance High force metalization Laboratory, hence is available should be used Ter-Fe-NOL). For for long best efficiency, the electromigration actuator should be lifetime and low pre-stressed to resistivity approx. 8 MPa. Pre- stressing may be required Surface Ink under positive Low Requires Silverbrook, tension pressure is held in power supplementary EP 0771 658 reduction a nozzle by surface consumption force to effect A2 and related tension. The Simple drop separation patent surface tension of construction Requires applications the ink is reduced No special ink below the bubble unusual surfactants threshold, causing materials Speed may the ink to egress required in be limited by from the nozzle. fabrication surfactant High properties efficiency Easy extension from single nozzles to page width print heads Viscosity The ink viscosity Simple Requires Silverbrook, reduction is locally reduced construction supplementary EP 0771 658 to select which No force to effect A2 and related drops are to be unusual drop separation patent ejected. A materials Requires applications viscosity reduction required in special ink can be achieved fabrication viscosity electrothermally Easy properties with most inks, but extension from High special inks can be single nozzles to speed is difficult engineered for a page width print to achieve 100:1 viscosity heads Requires reduction. oscillating ink pressure A high temperature difference (typically 80 degrees) is required Acoustic An acoustic wave Can Complex 1993 is generated and operate without drive circuitry Hadimioglu et focussed upon the a nozzle plate Complex al, EUP 550,192 drop ejection fabrication 1993 region. Low Elrod et al, EUP efficiency 572,220 Poor control of drop position Poor control of drop volume Thermo- An actuator which Low Efficient IJ03, IJ09, elastic relies upon power aqueous IJ17, IJ18, IJ19, bend differential consumption operation IJ20, IJ21, IJ22, actuator thermal expansion Many ink requires a IJ23, IJ24, IJ27, upon Joule heating types can be thermal insulator IJ28, IJ29, IJ30, is used. used on the hot side IJ31, IJ32, IJ33, Simple Corrosion IJ34, IJ35, IJ36, planar prevention can IJ37, IJ38, IJ39, fabrication be difficult IJ40, IJ41 Small chip Pigmented area required for inks may be each actuator infeasible, as Fast pigment particles operation may jam the High bend actuator efficiency CMOS compatible voltages and currents Standard MEMS processes can be used Easy extension from single nozzles to page width print heads High CTE A material with a High force Requires IJ09, IJ17, thermo- very high can be generated special material IJ18, IJ20, IJ21, elastic coefficient of Three (e.g. PTFE) IJ22, IJ23, IJ24, actuator thermal expansion methods of Requires a IJ27, IJ28, IJ29, (CTE) such as PTFE deposition PTFE deposition IJ30, IJ31, IJ42, polytetrafluoroethylene are under process, which is IJ43, IJ44 (PTFE) is development: not yet standard used. As high CTE chemical vapor in ULSI fabs materials are deposition PTFE usually non- (CVD), spin deposition conductive, a coating, and cannot be heater fabricated evaporation followed with from a conductive PTFE is a high temperature material is candidate for (above 350° C.) incorporated. A 50 μm low dielectric processing long PTFE constant Pigmented bend actuator with insulation in inks may be polysilicon heater ULSI infeasible, as and 15 mW power Very low pigment particles input can provide power may jam the 180 μN force and consumption bend actuator 10 μm deflection. Many ink Actuator motions types can be include: used Bend Simple Push planar Buckle fabrication Rotate Small chip area required for each actuator Fast operation High

Conductive A polymer with a High force Requires IJ24 polymer high coefficient of can be generated special materials thermo- thermal expansion Very low development elastic (such as PTFE) is power (High CTE actuator doped with consumption conductive conducting Many ink polymer) substances to types can be Requires a increase its used PTFE deposition conductivity to Simple process, which is about 3 orders of planar not yet standard magnitude below fabrication in ULSI fabs that of copper. The Small chip PTFE conducting area required for deposition polymer expands each actuator cannot be when resistively Fast followed with heated. operation high temperature Examples of High (above 350° C.) conducting efficiency processing dopants include: CMOS Evaporation Carbon nanotubes compatible and CVD Metal fibers voltages and deposition Conductive currents techniques polymers such as Easy cannot be used doped extension from Pigmented polythiophene single nozzles to inks may be Carbon granules page width print infeasible, as heads pigment particles may jam the bend actuator Shape A shape memory High force Fatigue IJ26 memory alloy such as TiNi is available limits maximum alloy (also known as (stresses of number of cycles Nitinol —Nickel hundreds of Low strain Titanium alloy MPa) (1%) is required developed at the Large to extend fatigue Naval Ordnance strain is resistance Laboratory) is available (more Cycle rate thermally switched than 3%) limited by heat between its weak High removal martensitic state corrosion Requires and its high resistance unusual stiffness austenitic Simple materials (TiNi) state. The shape of construction The latent the actuator in its Easy heat of martensitic state is extension from transformation deformed relative single nozzles to must be to the austenitic page width print provided shape. The shape heads High change causes Low current operation ejection of a drop. voltage Requires operation pre-stressing to distort the martensitic state Linear Linear magnetic Linear Requires IJ12 Magnetic actuators include Magnetic unusual Actuator the Linear actuators can be semiconductor Induction Actuator constructed with materials such as (LIA), Linear high thrust, long soft magnetic Permanent Magnet travel, and high alloys (e.g. Synchronous efficiency using CoNiFe) Actuator planar Some (LPMSA), Linear semiconductor varieties also Reluctance fabrication require Synchronous techniques permanent Actuator (LRSA), Long magnetic Linear Switched actuator travel is materials such as Reluctance available Neodymium iron Actuator (LSRA), Medium boron (NdFeB) and the Linear force is available Requires Stepper Actuator Low complex multi- (LSA). voltage phase drive operation circuitry High current operation

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BASIC OPERATION MODE Description Advantages Disadvantages Examples Actuator This is the Simple Drop Thermal directly simplest mode of operation repetition rate is ink jet pushes operation: the No usually limited Piezoelectric ink actuator directly external fields to around 10 kHz. ink jet supplies sufficient required However, IJ01, IJ02, kinetic energy to Satellite this is not IJ03, IJ04, IJ05, expel the drop. drops can be fundamental to IJ06, IJ07, IJ09, The drop must avoided if drop the method, but IJ11, IJ12, IJ14, have a sufficient velocity is less is related to the IJ16, IJ20, IJ22, velocity to than 4 m/s refill method IJ23, IJ24, IJ25, overcome the Can be normally used IJ26, IJ27, IJ28, surface tension. efficient, All of the IJ29, IJ30, IJ31, depending upon drop kinetic IJ32, IJ33, IJ34, the actuator used energy must be IJ35, IJ36, IJ37, provided by the IJ38, IJ39, IJ40, actuator IJ41, IJ42, IJ43, Satellite IJ44 drops usually form if drop velocity is greater than 4.5 m/s Proximity The drops to be Very Requires Silverbrook, printed are simple print close proximity EP 0771 658 selected by some head fabrication between the A2 and related manner (e.g. can be used print head and patent thermally induced The drop the print media applications surface tension selection means or transfer roller reduction of does not need to May pressurized ink). provide the require two print Selected drops are energy required heads printing separated from the to separate the alternate rows of ink in the nozzle drop from the the image by contact with the nozzle Monolithic print medium or a color print transfer roller. heads are difficult Electro- The drops to be Very Requires Silverbrook, static pull printed are simple print very high EP 0771 658 on ink selected by some head fabrication electrostatic field A2 and related manner (e.g. can be used Electrostatic patent thermally induced The drop field for small applications surface tension selection means nozzle sizes is Tone-Jet reduction of does not need to above air pressurized ink). provide the breakdown Selected drops are energy required Electrostatic separated from the to separate the field may ink in the nozzle drop from the attract dust by a strong electric nozzle field. Magnetic The drops to be Very Requires Silverbrook, pull on printed are simple print magnetic ink EP 0771 658 ink selected by some head fabrication Ink colors A2 and related manner (e.g. can be used other than black patent thermally induced The drop are difficult applications surface tension selection means Requires reduction of does not need to very high pressurized ink). provide the magnetic fields Selected drops are energy required separated from the to separate the ink in the nozzle drop from the by a strong nozzle magnetic field acting on the magnetic ink. Shutter The actuator High Moving IJ13, IJ17, moves a shutter to speed (>50 kHz) parts are IJ21 block ink flow to operation can be required the nozzle. The ink achieved due to Requires pressure is pulsed reduced refill ink pressure at a multiple of the time modulator drop ejection Drop Friction frequency. timing can be and wear must very accurate be considered The Stiction is actuator energy possible can be very low Shuttered The actuator Actuators Moving IJ08, IJ15, grill moves a shutter to with small travel parts are IJ18, IJ19 block ink flow can be used required through a grill to Actuators Requires the nozzle. The with small force ink pressure shutter movement can be used modulator need only be equal High Friction to the width of the speed (>50 kHz) and wear must grill holes. operation can be be considered achieved Stiction is possible Pulsed A pulsed magnetic Extremely Requires IJ10 magnetic field attracts an low energy an external pull on ‘ink pusher’ at the operation is pulsed magnetic ink drop ejection possible field pusher frequency. An No heat Requires actuator controls a dissipation special materials catch, which problems for both the prevents the ink actuator and the pusher from ink pusher moving when a Complex drop is not to be construction ejected.

AUXILIARY MECHANISM (APPLIED TO ALL NOZZLES) Description Advantages Disadvantages Examples None The actuator Simplicity Drop Most ink directly fires the of construction ejection energy jets, including ink drop, and there Simplicity must be supplied piezoelectric and is no external field of operation by individual thermal bubble. or other Small nozzle actuator IJ01, IJ02, mechanism physical size IJ03, IJ04, IJ05, required. IJ07, IJ09, IJ11, IJ12, IJ14, IJ20, IJ22, IJ23, IJ24, IJ25, IJ26, IJ27, IJ28, IJ29, IJ30, IJ31, IJ32, IJ33, IJ34, IJ35, IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Oscillating The ink pressure Oscillating Requires Silverbrook, ink oscillates, ink pressure can external ink EP 0771 658 pressure providing much of provide a refill pressure A2 and related (including the drop ejection pulse, allowing oscillator patent acoustic energy. The higher operating Ink applications stimulation) actuator selects speed pressure phase IJ08, IJ13, which drops are to The and amplitude IJ15, IJ17, IJ18, be fired by actuators may must be IJ19, IJ21 selectively operate with carefully blocking or much lower controlled enabling nozzles. energy Acoustic The ink pressure Acoustic reflections in the oscillation may be lenses can be ink chamber achieved by used to focus the must be vibrating the print sound on the designed for head, or preferably nozzles by an actuator in the ink supply. Media The print head is Low Precision Silverbrook, proximity placed in close power assembly EP 0771 658 proximity to the High required A2 and related print medium. accuracy Paper patent Selected drops Simple fibers may cause applications protrude from the print head problems print head further construction Cannot than unselected print on rough drops, and contact substrates the print medium. The drop soaks into the medium fast enough to cause drop separation. Transfer Drops are printed High Bulky Silverbrook, roller to a transfer roller accuracy Expensive EP 0771 658 instead of straight Wide Complex A2 and related to the print range of print construction patent medium. A substrates can be applications transfer roller can used Tektronix also be used for Ink can be hot melt proximity drop dried on the piezoelectric ink separation. transfer roller jet Any of the IJ series Electro- An electric field is Low Field Silverbrook, static used to accelerate power strength required EP 0771 658 selected drops Simple for separation of A2 and related towards the print print head small drops is patent medium. construction near or above air applications breakdown Tone-Jet Direct A magnetic field is Low Requires Silverbrook, magnetic used to accelerate power magnetic ink EP 0771 658 field selected drops of Simple Requires A2 and related magnetic ink print head strong magnetic patent towards the print construction field applications medium. Cross The print head is Does not Requires IJ06, IJ16 magnetic placed in a require magnetic external magnet field constant magnetic materials to be Current field. The Lorenz integrated in the densities may be force in a current print head high, resulting in carrying wire is manufacturing electromigration used to move the process problems actuator. Pulsed A pulsed magnetic Very low Complex IJ10 magnetic field is used to power operation print head field cyclically attract a is possible construction paddle, which Small Magnetic pushes on the ink. print head size materials A small actuator required in print moves a catch, head which selectively prevents the paddle from moving.

ACTUATOR AMPLIFICATION OR MODIFICATION METHOD Description Advantages Disadvantages Examples None No actuator Operational Many Thermal mechanical simplicity actuator Bubble Ink jet amplification is mechanisms IJ01, IJ02, used. The actuator have insufficient IJ06, IJ07, IJ16, directly drives the travel, or IJ25, IJ26 drop ejection insufficient process. force, to efficiently drive the drop ejection process Differential An actuator Provides High Piezoelectric expansion material expands greater travel in stresses are IJ03, IJ09, bend more on one side a reduced print involved IJ17, IJ18, IJ19, actuator than on the other. head area Care must IJ20, IJ21, IJ22, The expansion be taken that the IJ23, IJ24, IJ27, may be thermal, materials do not IJ29, IJ30, IJ31, piezoelectric, delaminate IJ32, IJ33, IJ34, magnetostrictive, Residual IJ35, IJ36, IJ37, or other bend resulting IJ38, IJ39, IJ42, mechanism. The from high IJ43, IJ44 bend actuator temperature or converts a high high stress force low travel during formation actuator mechanism to high travel, lower force mechanism. Transient A trilayer bend Very good High IJ40, IJ41 bend actuator where the temperature stresses are actuator two outside layers stability involved are identical. This High Care must cancels bend due speed, as a new be taken that the to ambient drop can be fired materials do not temperature and before heat delaminate residual stress. The dissipates actuator only Cancels responds to residual stress of transient heating of formation one side or the other. Reverse The actuator loads Better Fabrication IJ05, IJ11 spring a spring. When the coupling to the complexity actuator is turned ink High off, the spring stress in the releases. This can spring reverse the force/distance curve of the actuator to make it compatible with the force/time requirements of the drop ejection. Actuator A series of thin Increased Increased Some stack actuators are travel fabrication piezoelectric ink stacked. This can Reduced complexity jets be appropriate drive voltage Increased IJ04 where actuators possibility of require high short circuits due electric field to pinholes strength, such as electrostatic and piezoelectric actuators. Multiple Multiple smaller Increases Actuator IJ12, IJ13, actuators actuators are used the force forces may not IJ18, IJ20, IJ22, simultaneously to available from add linearly, IJ28, IJ42, IJ43 move the ink. Each an actuator reducing actuator need Multiple efficiency provide only a actuators can be portion of the positioned to force required. control ink flow accurately Linear A linear spring is Matches Requires IJ15 Spring used to transform a low travel print head area motion with small actuator with for the spring travel and high higher travel force into a longer requirements travel, lower force Non- motion. contact method of motion transformation Coiled A bend actuator is Increases Generally IJ17, IJ21, actuator coiled to provide travel restricted to IJ34, IJ35 greater travel in a Reduces planar reduced chip area. chip area implementations Planar due to extreme implementations fabrication are relatively difficulty in easy to fabricate. other orientations. Flexure A bend actuator Simple Care must IJ10, IJ19, bend has a small region means of be taken not to IJ33 actuator near the fixture increasing travel exceed the point, which flexes of a bend elastic limit in much more readily actuator the flexure area than the remainder Stress of the actuator. distribution is The actuator very uneven flexing is Difficult effectively to accurately converted from an model with finite even coiling to an element analysis angular bend, resulting in greater travel of the actuator tip. Catch The actuator Very low Complex IJ10 controls a small actuator energy construction catch. The catch Very small Requires either enables or actuator size external force disables movement Unsuitable of an ink pusher for pigmented that is controlled inks in a bulk manner. Gears Gears can be used Low force, Moving IJ13 to increase travel low travel parts are at the expense of actuators can be required duration. Circular used Several gears, rack and Can be actuator cycles pinion, ratchets, fabricated using are required and other gearing standard surface More methods can be MEMS complex drive used. processes electronics Complex construction Friction, friction, and wear are possible Buckle A buckle plate can Very fast Must stay S. Hirata plate be used to change movement within elastic et al, “An Ink-jet a slow actuator achievable limits of the Head Using into a fast motion. materials for Diaphragm It can also convert long device life Microactuator”, a high force, low High Proc. IEEE travel actuator into stresses involved MEMS, February a high travel, Generally 1996, pp 418-423. medium force high power IJ18, IJ27 motion. requirement Tapered A tapered Linearizes Complex IJ14 magnetic magnetic pole can the magnetic construction pole increase travel at force/distance the expense of curve force. Lever A lever and Matches High IJ32, IJ36, fulcrum is used to low travel stress around the IJ37 transform a motion actuator with fulcrum with small travel higher travel and high force into requirements a motion with Fulcrum longer travel and area has no lower force. The linear lever can also movement, and reverse the can be used for a direction of travel. fluid seal Rotary The actuator is High Complex IJ28 impeller connected to a mechanical construction rotary impeller. A advantage Unsuitable small angular The ratio for pigmented deflection of the of force to travel inks actuator results in of the actuator a rotation of the can be matched impeller vanes, to the nozzle which push the ink requirements by against stationary varying the vanes and out of number of the nozzle. impeller vanes Acoustic A refractive or No Large area 1993 lens diffractive (e.g. moving parts required Hadimioglu et zone plate) Only al, EUP 550,192 acoustic lens is relevant for 1993 used to concentrate acoustic ink jets Elrod et al, EUP sound waves. 572,220 Sharp A sharp point is Simple Difficult Tone-jet conductive used to concentrate construction to fabricate point an electrostatic using standard field. VLSI processes for a surface ejecting ink-jet Only relevant for electrostatic ink jets

ACTUATOR MOTION Description Advantages Disadvantages Examples Volume The volume of the Simple High Hewlett- expansion actuator changes, construction in energy is Packard Thermal pushing the ink in the case of typically Ink jet all directions. thermal ink jet required to Canon achieve volume Bubblejet expansion. This leads to thermal stress, cavitation, and kogation in thermal ink jet implementations Linear, The actuator Efficient High IJ01, IJ02, normal to moves in a coupling to ink fabrication IJ04, IJ07, IJ11, chip direction normal to drops ejected complexity may IJ14 surface the print head normal to the be required to surface. The surface achieve nozzle is typically perpendicular in the line of motion movement. Parallel to The actuator Suitable Fabrication IJ12, IJ13, chip moves parallel to for planar complexity IJ15, IJ33,, IJ34, surface the print head fabrication Friction IJ35, IJ36 surface. Drop Stiction ejection may still be normal to the surface. Membrane An actuator with a The Fabrication 1982 push high force but effective area of complexity Howkins U.S. Pat. No. small area is used the actuator Actuator 4,459,601 to push a stiff becomes the size membrane that is membrane area Difficulty in contact with the of integration in ink. a VLSI process Rotary The actuator Rotary Device IJ05, IJ08, causes the rotation levers may be complexity IJ13, IJ28 of some element, used to increase May have such a grill or travel friction at a pivot impeller Small chip point area requirements Bend The actuator bends A very Requires 1970 when energized. small change in the actuator to be Kyser et al U.S. Pat. No. This may be due to dimensions can made from at 3,946,398 differential be converted to a least two distinct 1973 thermal expansion, large motion. layers, or to have Stemme U.S. Pat. No. piezoelectric a thermal 3,747,120 expansion, difference across IJ03, IJ09, magnetostriction, the actuator IJ10, IJ19, IJ23, or other form of IJ24, IJ25, IJ29, relative IJ30, IJ31, IJ33, dimensional IJ34, IJ35 change. Swivel The actuator Allows Inefficient IJ06 swivels around a operation where coupling to the central pivot. This the net linear ink motion motion is suitable force on the where there are paddle is zero opposite forces Small chip applied to opposite area sides of the paddle, requirements e.g. Lorenz force. Straighten The actuator is Can be Requires IJ26, IJ32 normally bent, and used with shape careful balance straightens when memory alloys of stresses to energized. where the ensure that the austenitic phase quiescent bend is is planar accurate Double The actuator bends One Difficult IJ36, IJ37, bend in one direction actuator can be to make the IJ38 when one element used to power drops ejected by is energized, and two nozzles. both bend bends the other Reduced directions way when another chip size. identical. element is Not A small energized. sensitive to efficiency loss ambient compared to temperature equivalent single bend actuators. Shear Energizing the Can Not 1985 actuator causes a increase the readily Fishbeck U.S. Pat. No. shear motion in the effective travel applicable to 4,584,590 actuator material. of piezoelectric other actuator actuators mechanisms Radial The actuator Relatively High force 1970 constriction squeezes an ink easy to fabricate required Zoltan U.S. Pat. No. reservoir, forcing single nozzles Inefficient 3,683,212 ink from a from glass Difficult constricted nozzle. tubing as to integrate with macroscopic VLSI processes structures Coil/ A coiled actuator Easy to Difficult IJ17, IJ21, uncoil uncoils or coils fabricate as a to fabricate for IJ34, IJ35 more tightly. The planar VLSI non-planar motion of the free process devices end of the actuator Small area Poor out- ejects the ink. required, of-plane stiffness therefore low cost Bow The actuator bows Can Maximum IJ16, IJ18, (or buckles) in the increase the travel is IJ27 middle when speed of travel constrained energized. Mechanically High force rigid required Push-Pull Two actuators The Not IJ18 control a shutter. structure is readily suitable One actuator pulls pinned at both for ink jets the shutter, and the ends, so has a which directly other pushes it. high out-of- push the ink plane rigidity Curl A set of actuators Good fluid Design IJ20, IJ42 inwards curl inwards to flow to the complexity reduce the volume region behind of ink that they the actuator enclose. increases efficiency Curl A set of actuators Relatively Relatively IJ43 outwards curl outwards, simple large chip area pressurizing ink in construction a chamber surrounding the actuators, and expelling ink from a nozzle in the chamber. Iris Multiple vanes High High IJ22 enclose a volume efficiency fabrication of ink. These Small chip complexity simultaneously area Not rotate, reducing suitable for the volume pigmented inks between the vanes. Acoustic The actuator The Large area 1993 vibration vibrates at a high actuator can be required for Hadimioglu et frequency. physically efficient al, EUP 550,192 distant from the operation at 1993 ink useful Elrod et al, EUP frequencies 572,220 Acoustic coupling and crosstalk Complex drive circuitry Poor control of drop volume and position None In various ink jet No Various Silverbrook, designs the moving parts other tradeoffs EP 0771 658 actuator does not are required to A2 and related move. eliminate patent moving parts applications Tone-jet

NOZZLE REFILL METHOD Description Advantages Disadvantages Examples Surface This is the normal Fabrication Low speed Thermal tension way that ink jets simplicity Surface ink jet are refilled. After Operational tension force Piezoelectric the actuator is simplicity relatively small ink jet energized, it compared to IJ01-IJ07, typically returns actuator force IJ10-IJ14, IJ16, rapidly to its Long refill IJ20, IJ22-IJ45 normal position. time usually This rapid return dominates the sucks in air total repetition through the nozzle rate opening. The ink surface tension at the nozzle then exerts a small force restoring the meniscus to a minimum area. This force refills the nozzle. Shuttered Ink to the nozzle High Requires IJ08, IJ13, oscillating chamber is speed common ink IJ15, IJ17, IJ18, ink provided at a Low pressure IJ19, IJ21 pressure pressure that actuator energy, oscillator oscillates at twice as the actuator May not the drop ejection need only open be suitable for frequency. When a or close the pigmented inks drop is to be shutter, instead ejected, the shutter of ejecting the is opened for 3 ink drop half cycles: drop ejection, actuator return, and refill. The shutter is then closed to prevent the nozzle chamber emptying during the next negative pressure cycle. Refill After the main High Requires IJ09 actuator actuator has speed, as the two independent ejected a drop a nozzle is actuators per second (refill) actively refilled nozzle actuator is energized. The refill actuator pushes ink into the nozzle chamber. The refill actuator returns slowly, to prevent its return from emptying the chamber again. Positive The ink is held a High refill Surface Silverbrook, ink slight positive rate, therefore a spill must be EP 0771 658 pressure pressure. After the high drop prevented A2 and related ink drop is ejected, repetition rate is Highly patent the nozzle possible hydrophobic applications chamber fills print head Alternative quickly as surface surfaces are for:, IJ01-IJ07, tension and ink required IJ10-IJ14, IJ16, pressure both IJ20, IJ22-IJ45 operate to refill the nozzle.

METHOD OF RESTRICTING BACK-FLOW THROUGH INLET Description Advantages Disadvantages Examples Long inlet The ink inlet Design Restricts Thermal channel channel to the simplicity refill rate ink jet nozzle chamber is Operational May result Piezoelectric made long and simplicity in a relatively ink jet relatively narrow, Reduces large chip area IJ42, IJ43 relying on viscous crosstalk Only drag to reduce partially inlet back-flow. effective Positive The ink is under a Drop Requires a Silverbrook, ink positive pressure, selection and method (such as EP 0771 658 pressure so that in the separation forces a nozzle rim or A2 and related quiescent state can be reduced effective patent some of the ink Fast refill hydrophobizing, applications drop already time or both) to Possible protrudes from the prevent flooding operation of the nozzle. of the ejection following: IJ01-IJ07, This reduces the surface of the IJ09-IJ12, pressure in the print head. IJ14, IJ16, IJ20, nozzle chamber IJ22,, IJ23-IJ34, which is required IJ36-IJ41, IJ44 to eject a certain volume of ink. The reduction in chamber pressure results in a reduction in ink pushed out through the inlet. Baffle One or more The refill Design HP baffles are placed rate is not as complexity Thermal Ink Jet in the inlet ink restricted as the May Tektronix flow. When the long inlet increase piezoelectric ink actuator is method. fabrication jet energized, the Reduces complexity (e.g. rapid ink crosstalk Tektronix hot movement creates melt eddies which Piezoelectric restrict the flow print heads). through the inlet. The slower refill process is unrestricted, and does not result in eddies. Flexible In this method Significantly Not Canon flap recently disclosed reduces back- applicable to restricts by Canon, the flow for edge- most ink jet inlet expanding actuator shooter thermal configurations (bubble) pushes on ink jet devices Increased a flexible flap that fabrication restricts the inlet. complexity Inelastic deformation of polymer flap results in creep over extended use Inlet filter A filter is located Additional Restricts IJ04, IJ12, between the ink advantage of ink refill rate IJ24, IJ27, IJ29, inlet and the filtration May result IJ30 nozzle chamber. Ink filter in complex The filter has a may be construction multitude of small fabricated with holes or slots, no additional restricting ink process steps flow. The filter also removes particles which may block the nozzle. Small The ink inlet Design Restricts IJ02, IJ37, inlet channel to the simplicity refill rate IJ44 compared nozzle chamber May result to nozzle has a substantially in a relatively smaller cross large chip area section than that of Only the nozzle, partially resulting in easier effective ink egress out of the nozzle than out of the inlet. Inlet A secondary Increases Requires IJ09 shutter actuator controls speed of the ink- separate refill the position of a jet print head actuator and shutter, closing off operation drive circuit the ink inlet when the main actuator is energized. The inlet The method avoids Back-flow Requires IJ01, IJ03, is located the problem of problem is careful design to 1J05, IJ06, IJ07, behind inlet back-flow by eliminated minimize the IJ10, IJ11, IJ14, the ink- arranging the ink- negative IJ16, IJ22, IJ23, pushing pushing surface of pressure behind IJ25, IJ28, IJ31, surface the actuator the paddle IJ32, IJ33, IJ34, between the inlet IJ35, IJ36, IJ39, and the nozzle. IJ40, IJ41 Part of The actuator and a Significant Small IJ07, IJ20, the wall of the ink reductions in increase in IJ26, IJ38 actuator chamber are back-flow can be fabrication moves to arranged so that achieved complexity shut off the motion of the Compact the inlet actuator closes off designs possible the inlet. Nozzle In some Ink back- None Silverbrook, actuator configurations of flow problem is related to ink EP 0771 658 does not ink jet, there is no eliminated back-flow on A2 and related result in expansion or actuation patent ink back- movement of an applications flow actuator which Valve-jet may cause ink Tone-jet back-flow through the inlet.

NOZZLE CLEARING METHOD Description Advantages Disadvantages Examples Normal All of the nozzles No added May not Most ink nozzle are fired complexity on be sufficient to jet systems firing periodically, the print head displace dried IJ01, IJ02, before the ink has ink IJ03, IJ04, IJ05, a chance to dry. IJ06, IJ07, IJ09, When not in use IJ10, IJ11, IJ12, the nozzles are IJ14, IJ16, IJ20, sealed (capped) IJ22, IJ23, IJ24, against air. IJ25, IJ26, IJ27, The nozzle firing IJ28, IJ29, IJ30, is usually IJ31, IJ32, IJ33, performed during a IJ34, IJ36, IJ37, special clearing IJ38, IJ39, IJ40,, cycle, after first IJ41, IJ42, IJ43, moving the print IJ44,, IJ45 head to a cleaning station. Extra In systems which Can be Requires Silverbrook, power to heat the ink, but do highly effective higher drive EP 0771 658 ink heater not boil it under if the heater is voltage for A2 and related normal situations, adjacent to the clearing patent nozzle clearing can nozzle May applications be achieved by require larger over-powering the drive transistors heater and boiling ink at the nozzle. Rapid The actuator is Does not Effectiveness May be succession fired in rapid require extra depends used with: IJ01, of succession. In drive circuits on substantially IJ02, IJ03, IJ04, actuator some the print head upon the IJ05, IJ06, IJ07, pulses configurations, this Can be configuration of IJ09, IJ10, IJ11, may cause heat readily the ink jet nozzle IJ14, IJ16, IJ20, build-up at the controlled and IJ22, IJ23, IJ24, nozzle which boils initiated by IJ25, IJ27, IJ28, the ink, clearing digital logic IJ29, IJ30, IJ31, the nozzle. In other IJ32, IJ33, IJ34, situations, it may IJ36, IJ37, IJ38, cause sufficient IJ39, IJ40, IJ41, vibrations to IJ42, IJ43, IJ44, dislodge clogged IJ45 nozzles. Extra Where an actuator A simple Not May be power to is not normally solution where suitable where used with: IJ03, ink driven to the limit applicable there is a hard IJ09, IJ16, IJ20, pushing of its motion, limit to actuator IJ23, IJ24, IJ25, actuator nozzle clearing movement IJ27, IJ29, IJ30, may be assisted by IJ31, IJ32, IJ39, providing an IJ40, IJ41, IJ42, enhanced drive IJ43, IJ44, IJ45 signal to the actuator. Acoustic An ultrasonic A high High IJ08, IJ13, resonance wave is applied to nozzle clearing implementation IJ15, IJ17, IJ18, the ink chamber. capability can be cost if system IJ19, IJ21 This wave is of an achieved does not already appropriate May be include an amplitude and implemented at acoustic actuator frequency to cause very low cost in sufficient force at systems which the nozzle to clear already include blockages. This is acoustic easiest to achieve actuators if the ultrasonic wave is at a resonant frequency of the ink cavity. Nozzle A microfabricated Can clear Accurate Silverbrook, clearing plate is pushed severely clogged mechanical EP 0771 658 plate against the nozzles alignment is A2 and related nozzles. The plate required patent has a post for Moving applications every nozzle. A parts are post moves required through each There is nozzle, displacing risk of damage dried ink. to the nozzles Accurate fabrication is required Ink The pressure of the May be Requires May be pressure ink is temporarily effective where pressure pump used with all IJ pulse increased so that other methods or other pressure series ink jets ink streams from cannot be used actuator all of the nozzles. Expensive This may be used Wasteful in conjunction of ink with actuator energizing. Print A flexible ‘blade’ Effective Difficult Many ink head is wiped across the for planar print to use if print jet systems wiper print head surface. head surfaces head surface is The blade is Low cost non-planar or usually fabricated very fragile from a flexible Requires polymer, e.g. mechanical parts rubber or synthetic Blade can elastomer. wear out in high volume print systems Separate A separate heater Can be Fabrication Can be ink is provided at the effective where complexity used with many boiling nozzle although other nozzle IJ series ink jets heater the normal drop clearing methods ejection cannot be used mechanism does Can be not require it. The implemented at heaters do not no additional require individual cost in some ink drive circuits, as jet many nozzles can configurations be cleared simultaneously, and no imaging is required.

NOZZLE PLATE CONSTRUCTION Description Advantages Disadvantages Examples Electro- A nozzle plate is Fabrication High Hewlett formed separately simplicity temperatures and Packard Thermal nickel fabricated from pressures are Ink jet electroformed required to bond nickel, and bonded nozzle plate to the print head Minimum chip. thickness constraints Differential thermal expansion Laser Individual nozzle No masks Each hole Canon ablated or holes are ablated required must be Bubblejet drilled by an intense UV Can be individually 1988 polymer laser in a nozzle quite fast formed Sercel et al., plate, which is Some Special SPIE, Vol. 998 typically a control over equipment Excimer Beam polymer such as nozzle profile is required Applications, pp. polyimide or possible Slow 76-83 polysulphone Equipment where there are 1993 required is many thousands Watanabe et al., relatively low of nozzles per U.S. Pat. No. 5,208,604 cost print head May produce thin burrs at exit holes Silicon A separate nozzle High Two part K. Bean, micro- plate is accuracy is construction IEEE machined micromachined attainable High cost Transactions on from single crystal Requires Electron silicon, and precision Devices, Vol. bonded to the print alignment ED-25, No. 10, head wafer. Nozzles 1978, pp 1185-1195 may be clogged Xerox by adhesive 1990 Hawkins et al., U.S. Pat. No. 4,899,181 Glass Fine glass No Very small 1970 capillaries capillaries are expensive nozzle sizes are Zoltan U.S. Pat. No. drawn from glass equipment difficult to form 3,683,212 tubing. This required Not suited method has been Simple to for mass used for making make single production individual nozzles, nozzles but is difficult to use for bulk manufacturing of print heads with thousands of nozzles. Monolithic, The nozzle plate is High Requires Silverbrook, surface deposited as a accuracy (<1 μm) sacrificial layer EP 0771 658 micro- layer using Monolithic under the nozzle A2 and related machined standard VLSI Low cost plate to form the patent using deposition Existing nozzle chamber applications VLSI techniques. processes can be Surface IJ01, IJ02, litho- Nozzles are etched used may be fragile to IJ04, IJ11, IJ12, graphic in the nozzle plate the touch IJ17, IJ18, IJ20, processes using VLSI IJ22, IJ24, IJ27, lithography and IJ28, IJ29, IJ30, etching. IJ31, IJ32, IJ33, IJ34, IJ36, IJ37, IJ38, IJ39, IJ40, IJ41, IJ42, IJ43, IJ44 Monolithic, The nozzle plate is High Requires IJ03, IJ05, etched a buried etch stop accuracy (<1 μm) long etch times IJ06, IJ07, IJ08, through in the wafer. Monolithic Requires a IJ09, IJ10, IJ13, substrate Nozzle chambers Low cost support wafer IJ14, IJ15, IJ16, are etched in the No IJ19, IJ21, IJ23, front of the wafer, differential IJ25, IJ26 and the wafer is expansion thinned from the backside. Nozzles are then etched in the etch stop layer. No nozzle Various methods No Difficult Ricoh plate have been tried to nozzles to to control drop 1995 Sekiya et al eliminate the become clogged position U.S. Pat. No. 5,412,413 nozzles entirely, to accurately 1993 prevent nozzle Crosstalk Hadimioglu et al clogging. These problems EUP 550,192 include thermal 1993 bubble Elrod et al EUP mechanisms and 572,220 acoustic lens mechanisms Trough Each drop ejector Reduced Drop IJ35 has a trough manufacturing firing direction through which a complexity is sensitive to paddle moves. Monolithic wicking. There is no nozzle plate. Nozzle slit The elimination of No Difficult 1989 Saito instead of nozzle holes and nozzles to to control drop et al U.S. Pat. No. individual replacement by a become clogged position 4,799,068 nozzles slit encompassing accurately many actuator Crosstalk positions reduces problems nozzle clogging, but increases crosstalk due to ink surface waves

DROP EJECTION DIRECTION Description Advantages Disadvantages Examples Edge Ink flow is along Simple Nozzles Canon (‘edge the surface of the construction limited to edge Bubblejet 1979 shooter’) chip, and ink drops No silicon High Endo et al GB are ejected from etching required resolution is patent 2,007,162 the chip edge. Good heat difficult Xerox sinking via Fast color heater-in-pit substrate printing requires 1990 Hawkins et Mechanically one print head al U.S. Pat. No. strong per color 4,899,181 Ease of Tone-jet chip handing Surface Ink flow is along No bulk Maximum Hewlett- (‘roof the surface of the silicon etching ink flow is Packard TIJ shooter’) chip, and ink drops required severely 1982 Vaught et are ejected from Silicon restricted al U.S. Pat. No. the chip surface, can make an 4,490,728 normal to the effective heat IJ02, IJ11, plane of the chip. sink IJ12, IJ20, IJ22 Mechanical strength Through Ink flow is through High ink Requires Silverbrook, chip, the chip, and ink flow bulk silicon EP 0771 658 forward drops are ejected Suitable etching A2 and related (‘up from the front for page width patent shooter’) surface of the chip. print heads applications High IJ04, IJ17, nozzle packing IJ18, IJ24, IJ27-IJ45 density therefore low manufacturing cost Through Ink flow is through High ink Requires IJ01, IJ03, chip, the chip, and ink flow wafer thinning IJ05, IJ06, IJ07, reverse drops are ejected Suitable Requires IJ08, IJ09, IJ10, (‘down from the rear for page width special handling IJ13, IJ14, IJ15, shooter’) surface of the chip. print heads during IJ16, IJ19, IJ21, High manufacture IJ23, IJ25, IJ26 nozzle packing density therefore low manufacturing cost Through Ink flow is through Suitable page width Epson actuator the actuator, which for piezoelectric print heads Stylus is not fabricated as print heads require several Tektronix part of the same thousand hot melt substrate as the connections to piezoelectric ink drive transistors. drive circuits jets Cannot be manufactured in standard CMOS fabs Complex assembly required

INK TYPE Description Advantages Disadvantages Examples Aqueous, Water based ink Environmentally Slow Most dye which typically friendly drying existing ink jets contains: water, No odor Corrosive All IJ dye, surfactant, Bleeds on series ink jets humectant, and paper Silverbrook, biocide. May EP 0771 658 Modern ink dyes strikethrough A2 and related have high water- Cockles patent fastness, light paper applications fastness Aqueous, Water based ink Environmentally Slow IJ02, IJ04, pigment which typically friendly drying IJ21, IJ26, IJ27, contains: water, No odor Corrosive IJ30 pigment, Reduced Pigment Silverbrook, surfactant, bleed may clog EP 0771 658 humectant, and Reduced nozzles A2 and related biocide. wicking Pigment patent Pigments have an Reduced may clog applications advantage in strikethrough actuator Piezoelectric reduced bleed, mechanisms ink-jets wicking and Cockles Thermal strikethrough. paper ink jets (with significant restrictions) Methyl MEK is a highly Very fast Odorous All IJ Ethyl volatile solvent drying Flammable series ink jets Ketone used for industrial Prints on (MEK) printing on various difficult surfaces substrates such such as aluminum as metals and cans. plastics Alcohol Alcohol based inks Fast Slight All IJ (ethanol, can be used where drying odor series ink jets 2-butanol, the printer must Operates Flammable and operate at at sub-freezing others) temperatures temperatures below the freezing Reduced point of water. An paper cockle example of this is Low cost in-camera consumer photographic printing. Phase The ink is solid at No drying High Tektronix change room temperature, time-ink viscosity hot melt (hot melt) and is melted in instantly freezes Printed ink piezoelectric ink the print head on the print typically has a jets before jetting. Hot medium ‘waxy’ feel 1989 melt inks are Almost Printed Nowak U.S. Pat. No. usually wax based, any print pages may 4,820,346 with a melting medium can be ‘block’ All IJ point around 80° C.. used Ink series ink jets After jetting No paper temperature may the ink freezes cockle occurs be above the almost instantly No curie point of upon contacting wicking occurs permanent the print medium No bleed magnets or a transfer roller. occurs Ink heaters No consume power strikethrough Long occurs warm-up time Oil Oil based inks are High High All IJ extensively used in solubility viscosity: this is series ink jets offset printing. medium for a significant They have some dyes limitation for use advantages in Does not in ink jets, which improved cockle paper usually require a characteristics on Does not low viscosity. paper (especially wick through Some short no wicking or paper chain and multi- cockle). Oil branched oils soluble dies and have a pigments are sufficiently low required. viscosity. Slow drying Micro- A microemulsion Stops ink Viscosity All IJ emulsion is a stable, self bleed higher than series ink jets forming emulsion High dye water of oil, water, and solubility Cost is surfactant. The Water, oil, slightly higher characteristic drop and amphiphilic than water based size is less than soluble dies can ink 100 nm, and is be used High determined by the Can surfactant preferred curvature stabilize pigment concentration of the surfactant. suspensions required (around 5%) 

1. An inkjet nozzle arrangement comprising: a wafer defining an ink chamber for holding ink; a chamber roof covering the ink chamber, the chamber roof comprising: an ink ejection port supported by a plurality of outwardly extending bridge members; and a plurality of elongate heater elements interleaved between the bridge members for causing ejection of ink held in the ink chamber through the ink ejection port.
 2. A nozzle arrangement as claimed in claim 1, wherein the heater elements are arranged to be generally circular and comprises a plurality of spaced apart serpentine stations which extend radially inward.
 3. A nozzle arrangement as claimed in claim 2, wherein each serpentine station is symmetric and comprises a mirrored pair of serpentine portions.
 4. A nozzle arrangement as claimed in claim 1, wherein the ends of the heater elements terminate in a pair of vias which are connected to a metal layer of the wafer.
 5. A nozzle arrangement as claimed in claim 1, wherein the ink chamber is generally funnel-shaped and tapers inwardly away from the chamber roof.
 6. A nozzle arrangement as claimed in claim 5, wherein the wafer further defines an ink supply inlet at an apex of the tapered ink chamber, the ink supply inlet being substantially aligned with the ink ejection port.
 7. A nozzle arrangement as claimed in claim 1, wherein each bridge member defines an ink flow guide rail. 